MCAL Spectrophotometry Instruments include q Cary 50 UVvis

MCAL Spectrophotometry Instruments include: q Cary 50 UV-vis Spectrophotometer q Eclipse Spectrofluorometer q HPLC Diode Array and Fluorescence q ICP-OES with CCD detection

Spectrophotometry • The instruments all have in common that they use the absorption or emission of light, in the form of electromagnetic radiation (EMR) as a means of measuring the presence and/or concentration of material in a solution.

Cary 50 and Eclipse

Cary 50 Spectrophotometer q Mainly used to measures concentration of an analyte in solution q Concentration based on absorption of light (incident minus final light beam) by analyte (Beer -Lambert law) at specific wavelength q Need standards due to different extinction coefficients of different analytes.

Concentration • Based on Beer’s Lambert Law that concentration is proportional to the absorption of certain energy in the form of light A(absorbance) = εcd ε = extinction coefficient (constant for each compound) d = path length of cuvette =1 cm c = concentration of analyte

Cary 50 Uv-Vis spectrophotometer Detector diodes Mirrors Cuvette holder Grating Xenon light Beam splitter

Grating Scan Grating motor

Varian Cary® 50 UV-Vis spectrophotometer • Dual beam (split beam), Czerny-Turner monochromator, 190– 1100 nm wavelength range, approximately 1. 5 nm • Lamp full spectrum Xe pulse lamp single source • quartz overcoated optics, room light immunity, central control by PC with Windows® interface. • Grating holographic, 27. 5 x 35 mm, 1200 lines/mm, blaze angle 8. 6° at 240 nm • Beam splitting system • Detectors 2 silicon diode detectors.

Czerny-Turner monochromator

Zenon Lamp

Xenon Flash Lamp Advantages • The maximum scan rate is 24, 000 nanometers (nm) per minute. • Scan 190– 1100 nm in less than 3 seconds. • Measure samples up to 3 Abs • The Xenon lamp has a very long lifetime— 3 x 109 flashes • Room-light immunity

Photosensitive Sample

Uv-Vis Experiment • The analysis involves solving a set of simultaneous equations which describe the absorbance behavior of a mixture of vitamins; B 1 (thiamine) and B 6 (pyridoxine) at different wavelengths. • The number of equations, and likewise the number of wavelengths, equals the number of components in the mixture

Scan of Vitamin B 1 and B 6 B 1

Simultaneous Equations Mixture of B 1 and B 6: A 245 = εB 1(245)CB 1 + εB 6(245)CB 6 A 290 = εB 6(290)CB 6 + εB 1(290)CB 1

Spectrofluorometer • Mainly used to measure the concentration of fluorescing compounds. • Advantage - high sensitivity • Disadvantage - low number of compounds fluoresce • But - can make compounds fluoresce by binding a fluorescent compound

Motors Grating ample holder Detector photomultiplier Gr Dr Filter Xenon lamp

Emmission monochromator Excitation monochromator Gratings Sample PMT Xenon lamp Reference PMT Beam splitter Sample holder (cuvette)

Emmission Scan Eclipse Spectrofluorometer

HPLC with Diode Array Detector Fluorescence detector Diode Array Detector

Diode Array • The diode array uses a broad emission light source • two diode arrays and dual-pathlength flow cells. • All the light is allowed to pass through the sensing cell • and subsequently the light is dispersed by means of a holographic grating and • the dispersed light allowed to fall on an array of diodes.

Diode Array

Diode Array • The light (photons)generated electric charge carriers discharges the diode capacitor • The amount of charge needed to recharge capacitors is proportional to number of photons detected by each diode, which is proportional to light intensity.

HPLC Experiment • Identification of unknown compounds by their retention time. • Determination of concentration by use of 1) external standard curve, 2) internal standard or standard 3) or standard addition.

Four view display shows the chromatogram, 3 D, absorbance and spectrum plots

Cary 50 Scan Caffeine 204 273

Diode Array Screen

Quinine and Caffeine Fluorescence detection Exc λ = 347, Em λ = 448 Quinine rt = 12. 1 Uv detection λ = 213, 273 Caffeine rt = 9. 6

HPLC Experiment - Light Sources • Fluorescence detector uses Xenon lamp which has wavelength region of 250 -600 • The HPLC Diode Array uses two lamps a deuterium lamp with wavelengths from 160 to 380 and tungsten halogen lamp which covers wavelengths from 240 to 2500.

HPLC Experiment Concentration Determined by External Standard

700 -ES Series Simultaneous ICP’s

ICP-OES Experiment • Determine the mineral content of solid samples of: – Grains – Mining rock – Water – Feeds and foods – Surfaces

Radial Plasma Central Channel Fireball Viewing Volume Viewing Height Work coil

Spraychambers Sturman-Masters -double pass Aerosol to Torch Sample Inlet Glass Cyclonic - smaller volume To Plasma Sample Flow To Drain Pump to Drain

Need source of excitation Need way of measuring light emission

Varian Simultaneous ICP Optics Detector Chip Prism Crossdisperser Light from Plasma Echelle Grating

Echelle Grating

Varian Simultaneous ICP Optics Torch Echelle Grating Detector Chip Prism Crossdisperser

720 -ES Series CCD Detector

Vista. Chip CCD detector • The CCD (charge coupled device) 70 000 pixels, arranged to exactly match the two dimensional image from the echelle optics. • continuous wavelength coverage from 167 – 785 nm. • trace and major concentrations can be measured simultaneously,

Motor Mirror

720 -ES Series CCD Detector 167 nm Order 88 Order 19 785 nm

Axial verses radial torch sensitivity

ICP Experiment • Determination of mineral content in commercial products (product labelling, nutrient requirements, mining). – Dry ashing of sample • Burns off organic material leaving ash (minerals) – Acid digestion of sample • Dissolves minerals or can dissolve total sample including organic material (wet ashing) • Concentration determined by external standard, standard addition, and internal standard.

Concentration of unknown Standard Addition